This invention is directed towards data communications over telephony and network systems, and more particularly towards dial-up services using PCM modem technology.
Improved Modem technology has greatly increased the speed in which data may be transmitted and received over point to point and multipoint connections. Modems that operate on digital connections (for example DSL, ISDN, etc.) can provide high throughput with minimal errors. However, for modems used over POTS (Plain Old Telephone System) lines, digital modems are not an option. Portions of PSTN (Public Switched Telephone Network) in the world still utilize analog lines, often in the form of twisted-pair copper wire carrying analog signals. Even if telephone central offices (COs) have a digital infrastructure through digital switches and backbones, the connections from the CO to residences are still over analog local loops. The analog local loop segment of POTS from CO to the residence which is referred to in the art as the xe2x80x9clast-milexe2x80x9d requires the use of analog modems for data connections. Digital connections using xDSL technologies maybe possible to connect the residences to COs, however, there are many restrictions, the services are usually at higher cost, and are not as widely available.
Currently, symmetric or asymmetric point-to-point analog dial-up connections up to 33.6 kbps (KiloBits Per Second) are possible using ITU (International Telecommunications Union) Recommendation V.34 modems. However, due to various impairments encountered connection rates may not be as high. Therefore, applications such as video communication (even with compression) may not be suitable for dial-up connections using V.34 speeds.
Given that the majority of today""s network is digital in nature, the newly adopted Standard ITU Recommendation V.90 utilizes the digital portions of the telephone network to provide data rates of up to 56 kbps (with theoretical speed limit of 64 kbps) in the downstream direction. The V.90 Standard incorporates Pulse Code Modulation (PCM) for the downstream direction of the data call to achieve the fastest data transmission rates possible. Due to technical challenges and the degree of difficulty, PCM was not considered in ITU Recommendation V.90 for the upstream direction. Instead, the upstream modulation is performed according to ITU Recommendation V.34, which has data transmission rate limits as previously described.
ITU Recommendation V.90 provides asymmetrical data transmission rates that are quite appealing to Internet Service Providers (ISP) and clients when it comes to web browsing applications. In this context, the downstream direction is from a server to a client or user, and the upstream direction is from the client or user to the server.
ITU Recommendation V.90 specifies that network topology is such that one end is connected to the network digitally. Hence, rates and modulation schemes as defined by ITU Recommendation V.90 are not applicable when both ends are connected to the network via analog local loop. This is the case for majority of the residual users. Also, asymmetrical data transmission rates limit the usefulness of V.90 modems when it comes to applications such as interactive data services like video calls and interactive on-line gaming that require a fast connection rate in both the downstream and upstream directions.
As technologies continue to become more interactive, a premium may be placed on data transmission services that can provide near symmetrical rates, especially when both ends of the call are connected to network over POTS line. Consequently, the present model will become insufficient.
A method and apparatus are provided for achieving the fastest possible symmetric, near-symmetric, or user-configured data transmission rates between end sites which are connected to the network over POTS line and thereby require analog modems. The present invention includes a device, called a Multimedia Unit (MU), that takes advantage of PCM modem technology in both directions of the call to establish an appropriate (near symmetrical or nonsymmetrical) data transmission rate over point-to-point or multipoint dial-up connection. It can be located either at the phone company, Internet Service Provider (ISP), or a stand-alone gateway.
According to the present invention, MU is comprised of two digital modems (a first digital modem and a second digital modem) and a controller. The first and second digital modems and the controller may be physically co-located, or, may be partitioned into two sections. Each partition comprises a digital modem and a controller section. These partitions may be co-located or separated across the network. The controller sections can stay in contact via different means. For instance, direct wire in case of stand alone, and via Internet, or PSTN (Public Switched Telephone Network, also known as GSTN, General Switched Telephone Network) for the distributed case.
When a user wishes to establish a connection from a first analog modem to a second analog modem, the first analog modem calls the first digital modem. Next, the first digital modem establishes a connection with a second digital modem through the controller section. Then the second digital modem under direction of the controller section dials up the second analog modem. Subsequently, the controller instructs the digital modems to establish a connection at an appropriate or selectable data transmission rate. The first analog modem may dial the number to the second analog modem plus a prefix that will indicate to the controller the type of connection. Description and means to request such services are described in co-pending U.S. patent application Ser. No. 09/479,679 filed on Jan. 7, 2000 entitled xe2x80x9cA METHOD AND APPARATUS FOR PROVIDING AN AUTOMATED SELECTION OF A TELECOMMUNICATION SERVICE FROM AMONG A PLURALITY OF TELECOMMUNICATION SERVICESxe2x80x9d, assigned to Motorola, Inc. and incorporated herein by reference.
Depending on the requirements, this data transmission rate may be the fastest possible symmetric rate, which corresponds to the slowest analog modem transmit rate. Other possible data transmission rates include near-symmetrical, non-symmetrical, or user configured rates.
Advantages of the present invention include the ability to utilize Pulse Code Modulation (PCM) in the upstream direction to achieve fast data transmission rates. This in turn allows for providing the fastest possible symmetric or near-symmetric data transmission rates between two or more analog modems. Alternatively, it enables the user to request a specific type of connection. For example, a user can request a connection to handle video stream, or simply request a connection that meets the requirements for voice. The different type of service can be requested by means disclosed in the patent application Ser. No. 09/479,679, described hereinbefore, by dialing a certain prefix before the phone number. Telephone companies"" tariffs may change to account for the different type of dial-up services based on the connection rates.
Other advantages include the ability to perform point-to-multipoint connections utilizing PSTN digital infrastructure, but where the xe2x80x9clast milexe2x80x9d connections are still analog connections and end points are connected to the network over POTS lines via analog modems.